1. Field of the Disclosure
The present disclosure relates to a device for bonding a flexible PCB to a camera module.
2. Discussion of the Related Art
This section provides background information related to the present disclosure which is not necessarily prior art.
Generally, methods bonding polymer resin adhesive include an ultrasonic wave bonding method and a thermo-compression bonding method. An ultrasonic wave bonding device includes an ultrasonic vibrator generating ultrasonic wave, and an ultrasonic horn converting ultrasound generated by the ultrasonic vibrator to vibration energy to bond a bonding object.
That is, in a case the ultrasonic wave vibration energy is transmitted to the bonding object via the ultrasonic horn, an instant frictional heat is generated from an adhesive installed on an adhesive surface of the bonding object. The adhesive is melted by the frictional heat to bond the bonding object.
A thermo-compression bonding device mutually bonds fusing objects by applying heat and pressure thereto, and may take various shapes according to materials and shapes of the fusing objects. The thermo-compression bonding device generates heat using a power supply from an outside, and uses the heat to bond the bonding objects.
The ultrasonic wave and thermo-compression bonding devices use polymer resin adhesives when bonding the bonding objects, where a representative polymer resin adhesive is an ACF (Anisotropic Conductive Film, hereinafter referred to as conductive film). The ACF, consisting of an insulating adhesive polymer resin (matrix) with dispersed conductive particles, may be adhesive materials that simultaneously perform electrical interconnection of electrodes via conductive particles based on an insulating polymer resin and conductive particles dispersed in the polymer resin, and mechanical connection via thermal curing of the polymer resin.
In general, fine particles, such as gold, copper, nickel, carbon, a metal-coated polymer, an intrinsically conductive polymer and the like are used as conductive particles, and an epoxy resin, a polyimide resin, a silicon resin, an acrylic resin, a polyester resin or a polysulfone resin are used as a polymer resin. According to fields of application, the types of conductive particles may vary, and they may include non-conductive particles for the purpose of reducing a coefficient of thermal expansion.
In the method of interconnecting electronic components using an anisotropic conductive adhesive, there are advantages in that it is clean, simple and environmentally friendly because an existing soldering process is replaced with a lead-free process, it is more thermally stable because there is no need to apply the instantaneous temperature to the product (low temperature process), the cost of the process can be reduced by using a cheap substrate, such as a glass substrate or polyester flex, and an ultra-fine electrode pitch can be implemented via electrical connection using fine conductive particles.
The anisotropic conductive adhesives having these advantages are widely used in applications such as smart cards, liquid crystal displays (LCD), plasma display panels (PDP), display packaging of organic light emitting diodes, computers, portable telephones, communication systems and the like.
The anisotropic conductive adhesives are commonly used in display module mounting technologies for outer lead bonding (OLB) when connecting a flexible substrate to a glass substrate and for bonding the flexible substrate with a printed circuit board (PCB). The market for anisotropic conductive adhesives is growing rapidly.
In addition, the importance of anisotropic conductive adhesives is also increasing rapidly, in bonding processes of a COG (Chip On Glass), in which a driving circuit IC chip is directly connected to the glass substrate, and a COF (Chip On Film), in which a flip chip is directly connected to the flexible substrate, since a connection having an ultra-fine pitch is required due to the increasing densification and complexity of the driving circuit IC.
In the mounting technology of the electronic components using the anisotropic conductive adhesive, connection is achieved via electrical conduction of conductive particles between electrode pads using a thermo-compression process and thermo-setting of a polymer resin.
The thermo-setting polymer resin of conductive film gets faster in thermo-setting reaction speed as temperature rises, such that if the temperature rises high, a faster bonding operation can be performed. However, an excessive high temperature may cause several problems such as thermal deformation of conductive film and decreased in physical properties.
In addition, structurally weak structures such as camera modules of mobile terminals may be damaged due to high temperature and high pressure if applied with the ultrasonic wave and thermo-compression bonding processes. It is, therefore, desirable to overcome the above problems and others by providing a countermeasure to cope with these disadvantages.